This invention relates to the testing for faulty, therefore dangerous, performance of various types of zero speed indicators that are used to prevent a machine guard from being opened until the machine has come to a complete stop or has slowed sufficiently to prevent injury to anyone intending to access or work on the machine in the guarded space. The testing methods, devices, processes and decisions on test outcomes, are constructed and arranged so that the indicators can be tested while the machine is running, preventing unnecessary production interruptions and machine shutdowns, as well as take advantage of scheduled and unscheduled machine shutdowns to perform the tests. By performing these tests the hazardous opening of a guard due to a faulty zero speed indication can thus be anticipated and prevented.
For additional safety, machine guard protective systems will sometimes utilize motion interference or blocking devices which are inserted in the motion path of a component of the stopped machine so that machine motion cannot take place while the guard is open. The present invention further relates to the testing of the insertion of motion interference or blocking devices in conjunction with zero speed indicators, both of which must perform correctly in order to permit the unlocking and opening of the guard.
Barrier guards, shields, covers, screens and the like are among the oldest known safeguards for protecting personnel from the hazards of moving machinery. Their effectiveness derives from three properties: they prevent entry of the body into the zone of operation, they retain expelled missiles, and they define the safe from the unsafe portions of the machine. The need to access machinery leads to the removal or openings of barriers whereupon their concomitant protection is lost. Heretofore the shortcomings have been addressed by interlocks, which provide a connection between a barrier and the control or power system of the machinery to which the barrier is fitted. The interlock and the barrier with which it operates is designed, installed and adjusted so that until the barrier guard is closed into its protective state the interlock prevents the machinery from operating by interrupting the power medium and also so that opening of the barrier causes the hazard to be eliminated before access is possible or it may be necessary that the barrier remain closed and locked until the risk of injury from the hazard has passed.
The barrier locking system wherein the barrier is to remain locked until the risk of injury from the hazard has passed is necessary when either 1) simply opening or removing the guard does not eliminate the hazard before access is possible or 2) opening a guard other than at predetermined points in the machine cycle may expose the hazard.
The guard locking system will normally consist of a timing device or motion or position sensing device and a guard locking device. These may be individual units or combined in one assembly. Variable conditions of operation of machinery produce variable amounts of run down and in these circumstances a timing device may be inappropriate to determine when the run down has reached a non-hazardous state since it has to be set for the longest run down time that might be expected. The variable time element may, however, be eliminated by the use of a motion or position sensing device, which allows the guard to be opened as soon as the hazard is no longer present.
Available on the market today are a number of position, motion, timing and guard locking devices that operate on various principles. Among motion and position sensing devices some may suffer from the disadvantage that they show poor response at low speed and are therefore acceptable only where residual motion after the guard has been opened could not cause injury. On the other hand, where injury could result from residual motion, more sensitive devices and or timing devices may be necessary. Examples of typical motion or position sensing devices are a) rotation sensing devices that may operate on centrifugal force, friction , eddy current generation, voltage generation, optical or electronic pulse generation b) photo-electric beam c) proximity devices or d) position switches or valves.
Timing device examples include a) mechanical electrical or electronic clocks b) delay relays c) sequence valves d) threaded bolt or e) a dashpot.
Examples of typical guard locking devices are a) a captive-key unit b) a trapped-key unit c) mechanical bolt or d) shotbolts which may be solenoid operated, hydraulic or pneumatic.
The present invention relates to the testing of motion sensing devices that indicate zero speed or the cessation of motion. These devices actively monitor moving machine elements and are never benign when the machine is active. Such indicating devices may wear out or get out o f adjustment or otherwise fail by prematurely signaling that motion has been arrested. This leads to unlatching of the barrier guards before the motion has ceased and before entry to the protected regions is safe. A statistically significant number of people will depend on the efficacy of the motion detectors to unlock guards when it may not be safe to do so.
To help prevent a false sense of security, it is desirable to improve the reliability of motion detectors and reliance thereon by regularly testing them. The dependence on zero speed systems is entirely analogous to the public""s reliance on the xe2x80x9csafety edgesxe2x80x9d on ordinary elevator doors.
Zero speed indicators may be completely removed from machines and tested by methods specified by the manufacturers. This procedure is practical only when infrequent inspections are anticipated and when the safety of the basic machine is not compromised by the removal of the motion indicator such as during a general machine shutdown.
The present invention describes a process whereby the motion detectors are frequently and automatically tested in situ while the machinery is in motion (and production) and while total personnel protection is assured. A further novel process is envisioned where the motion detectors are automatically tested in situ whenever the machine is shut down, such as when control systems stop switches are activated for lunch breaks, routine cleaning, maintenance or end-of-shift, when emergency stop devices are employed, when power disconnect is effected; or when latchless interlocked barriers are opened. In addition, when the motion detector indicates that the moving parts have stopped, it may be desired that absolute safety he insured by requiring a motion blocking member to be insertable and inserted between the now stopped moving parts before a guard protecting such parts can be opened.
There are many applications of safety closures or barriers that must remain closed and locked until the dangerous components that are guarded come to a stop. In such situations it is usual to employ run down completion detection devices such as motion detectors, zero speed switches indicators or detectors, timing devices, delay devices, interference devices, and motion blockers to make a final check to determine that the machine has in fact come to the required stop.
The present invention is directed to the testing of zero speed indicators and the incorporation of interference or motion blocking devices into the overall testing process of guard closures whether such closures are used separately from or in conjunction with interlocks, closure locks, zero speed indicators, and various testing devices. The testing, methods of testing, testing process, testing systems and devices for interlocks, guard closures and closure locks have been extensively detailed in two patent applications filed in the names of the two inventors of the present invention. These applications are incorporated by reference into the present application and set forth in detail the testing, methods of testing, testing processes testing systems and devices for interlocks, guard closures and closure locks. One application has Ser. No. 08/861,328, filed on May 21, 1997 now U.S. Pat. No. 5,870,317, entitled REMOTE AND PROXIMAL INTERLOCK TESTING MECHANISM AND TESTING SYSTEMS. The other application has Ser. No. 09/033,322 and was filed on Mar. 2, 1998 and is entitled REMOTE AND PROXIMAL GUARD TESTING SYSTEMS AND TESTING SYSTEMS EITHER SEPARATELY OR IN CONJUNCTION WITH INTERLOCK TESTING MECHANISMS AND SYSTEMS.
By way of reference, the above patent applications disclose the methods and means for testing in situ of guard interlocks, guard closures, and closure locks on machines, without stopping the machine or interrupting production to perform the tests, and the detection by the test of a fault in any of them does not lead to stopping of the machine unless so desired. If the machine is permitted to continue to run after the testing detects a fault or faults, remedial actions can be instituted to postpone repairs of the failures to a future convenient time. The interlocks are tested to determine whether any of them have failed, hence will not perform, as they should when called upon to execute their intended safeguarding functions. The guard closures are tested to determine whether any of them can be opened when they should be closed and locked to alert against a false sense of security that entry into the hazardous spaces they are meant to protect is prevented when it is not. The failure to prevent the guard closure from opening can be due to various causes. One of these can be the failure of its lock to keep the guard closure xe2x80x9cshutxe2x80x9d disclosing both a closure failure and a lock failure. Closure locks are also tested by direct means.
A zero speed indicator essentially consists of a device that will detect and indicate when the machine component speed it is measuring has come to the required stop, i.e., either has been reduced to zero or where applicable to a value sufficiently close to zero determined to be nonhazardous to personnel contact. In the present invention, unless otherwise indicated the term zero speed and its variants, means the required stop as defined above, and zero speed detectors are also zero speed indicators with both terms used synonymously. Furthermore, any one zero speed indicator may serve more than one guard closure protected space. Therefore, statements referring to one zero speed indicator and a guard closure and/or closure lock served by it, should be understood as referring to all guard closures and/or their locks served by the zero speed indicator.
The zero speed indicators are in some manner attached to the moving part of the machine being guarded and will be indicating the movement of the machine, and thus if they reflect a zero speed reading the guard may be opened. However, to open the guard with impunity it is essential that the zero speed indicators be periodically tested to make sure that when one relies on its indication of zero speed that in fact the machine has come to the required stop.
Normally, a zero speed indicator is attached to or driven by any component of a moving machine whose speed is proportional to the speed of the hazardous elements that require protection by guard closures. As the motion of the monitored component decreases to zero, the zero speed indicator has an opportunity to detect and signal the achievement of the required stop motion which, in turn, becomes a permissive or necessary condition for unlatching the guard closure.
The present invention includes a first novel process for testing the accuracy and reliability of the zero speed indicator while the machine component is running under power. In this process the zero speed indicator is temporarily uncoupled in situ, i.e., isolated from the monitored component by removing it or by declutching it from the component or by any other suitable means. Without the driving impetus from the machine component, the zero speed indicator will eventually run down to the required stop motion. If desired, the zero speed indicator may be decelerated by braking devices to save time. If the zero speed indicator is a device without integral speed rundown components, e.g. a photoelectric device, then such a zero speed indicator will have to be provided with a speed rundown component as part of the test setup. In the isolated state any known suitable testing methods or devices may be used to verify the accuracy of the zero speed indicators. If the zero speed indicator fails to operate properly, the guard closure lock should remain latched for the sake of safety until a repair has been completed. It may also be desirable to actuate xe2x80x9ctest failedxe2x80x9d warning indicators and devices, and in some circumstances, it may be desirable to shut the machine down while maintaining the interlock function and unlatching the guard closures so that maintenance may proceed unencumbered.
In accordance with the present invention the first novel process provides for testing the motion indicators in situ for accuracy and reliability, while the protected machine components are running under power. If the test determines that a motion indicator of a guard protected space will fail to indicate correctly the occurrence of a safe stop, it provides the great advantage of detecting this in advance of allowing a prospective opening of the guard and gives early warning of this prospective safety failure. With such warning available steps can be instituted and devices provided to maintain the protective guard locked, preventing a future entry into the hazardous space until a scheduled repair or replacement of the faulty motion indicator takes place. In contrast, the reliance on the motion indicator""s correct performance without testing it in advance fosters a false sense of security, and leads to the concomitant hazard of prematurely allowing a prospective entry into the guard protected space. With the preventive steps in place, the entry protection of the guarded space is secured, and the machine need not be stopped nor production disrupted upon detecting the motion indicator""s failure. Likewise, the machine can be stopped and allowed to be safely restarted as long as the access to the hazardous space continues to be barred. Repair and replacement of the failed motion indicator can be scheduled for whatever time is appropriate. The aforementioned novel process is designed to provide all of these novel advantages otherwise absent without it.
It should be noted that the novel motion detector verification test method or device used in the proposed process is not equivalent to a zero speed indicator system with a redundant motion indicator. Regardless of the level of redundancy, without the novel process of the present invention, failure of a motion detecting system can not be determined while the machinery is in powered operation. Consequently, advanced warning of such failure and the deployment of associated counter measures will not be possible.
In accordance with the present invention there is also provided a second novel process for testing zero speed indicators without interrupting the operation or production capability of the machine and without the need to uncouple the zero speed indicator from the monitored component.
This novel process applies to machines that operate with intermittent dangerous motions. Their zero speed detectors can readily be tested during the motion run down phase when the intrinsic or natural movements in the points or zones of operation are caused to come to rest as required by the machine operation process. An example may be found in the power press operating in the xe2x80x9csingle strokexe2x80x9d mode where its state repeatedly moves between clutching and declutching and braking.
In this regard it is important to note that every moving machine element has a xe2x80x9cspeed run downxe2x80x9d phase when required to stop. Therefore, the operation of zero speed indicators during intermittent stops are intrinsically no different than during any other machine stops.
Specifically, continuously operating machinery that are monitored by motion detectors achieve a state of rest whenever control stops are initiated or when emergency stops are executed or when lockout procedures call for power interruption. In such instances. analogous to the intermittent motion machines, it is possible to test the zero speed indicators during the machine""s run down to the state of rest without interrupting production or uncoupling of the zero speed indicators from the monitored components.
In the above referred to applications for testing zero speed indicators when machine stops are initiated a variety of known suitable testing methods or devices may be used to verify the accuracy of the zero speed indicators during the machine run down phase, including those employed for such verification testing in the first novel invention process previously described. Failure of the zero speed indicating system detected by the verification test will preclude the unlatching of the lock or locks of the guard closure or closures it serves. Only after repairs or replacements have restored the reliability of the motion detector to correctly indicate zero speed will it be trusted to give permission to unlatch the locks. With their guard locks latched, the affected hazardous spaces remain protected, denying entry to personnel. Hence the machine can be restarted and production can continue in spite of the presence of a known faulty motion detector. Furthermore, the repairs or replacements of the faulty motion detector can now be scheduled for what ever time is suitable.
Thus, the aforementioned second novel process provides for testing of the motion indicators in situ for accuracy and reliability, and the testing to be done while the protected machine components are in the xe2x80x9crunning downxe2x80x9d phase of a stop initiation. T his provides the advantage of being able to detect if a motion detector will fail to indicate correctly when the safe stop of the running down phase will occur, and to warn thereof in advance of a prospective opening of the guard. Having such warning available, steps can be instituted and devices provided to maintain the protective guard locked when such failure is detected, preventing entry into the hazardous space until a scheduled repair or replacement takes place, or until assurance is gained by other means that a safe stop is present. In contrast, the reliance on the motion detector""s correct performance without testing it fosters a false sense of security, and leads to the concomitant hazard of prematurely allowing entry into a guard protected space. With the preventive steps in place, the entry protection of the guarded space is secured and the machine can be stopped and allowed to be safely restarted to continue production as long as the access to the hazardous space continues to be barred. Repairs and replacements of the failed motion indicator can be scheduled for whatever time is appropriate. This novel process is designed to provide all of these novel advantages otherwise absent without it.
A third novel aspect of the present invention is associated with the insertion of blocking devices into the points or zones of operation or into synchronized power trains that will absolutely prohibit dangerous machine motions.
Interlocked and locked guard closures with zero speed monitoring capability are intended to protect personnel from hazardous moving mechanical elements regardless of whether the motion is attributable to external power sources or internal stored energy. Access to the operational zones protected by guard closures is granted only after hazardous motion has subsided. As a final step in operator protection, this invention anticipates situations where an interference system will be deployed in synchronized power transmission trains or into the zone of operation that will prevent all movement before a guard closure lock unlatches and allows the operators to place their bodies into the hazard zone. Die blocks and props are typical interference devices used in zones of operations. Application of the interference system must be preceded by the establishment of zero motion by a zero speed detection system. In the usual case, the zero speed system unlatches the guard closure lock once the motion ceases. The third novel invention will require that the guard closure locks do not unlatch and only permission to unlatch is granted by the zero speed system when it indicates that motion is terminated. Guard closure locks will then unlatch only if interference devices are fully inserted or deployed and if the associated protective status is communicated to the machine controller.
In summary, the third mentioned novel invention process operates as follows: When the zero speed detection system issues a signal that the motion has ceased the signal is to be utilized to command and execute the insertion of a motion interference device as a precursor to the unlatching of any interlocked and locked guard closures protecting the point of operation. This insertion will prevent, due to any cause, any motion to be present or resumed in the dancer zone after the guard closure has been unlatched and opened for access. If, after the zero speed signal has been issued, the interference device can not be inserted the most likely reason is that at the time of insertion zero motion was not present as indicated and that the motion hazard continues. This serves as a signal not to unlatch the guard closure.
The ultimate guard closure system contains interlocks and interlock testing systems, zero speed monitors with testing capabilities, guard closures with guard closure testing systems, locks with lock testing systems and interference devices with their testing systems. Unlatching of the guard closure usually requires the essentially simultaneously fulfillment of the following necessary conditions, 1) tests on guard closure locks have been passed, 2) tests on guard closures by force displacement devices have been passed, 3) tests on interlocks have been passed, 4) tester probe tests have been passed, 5) tests on zero speed indicators have been passed, 6) tests on timer or delay devices have been passed, 7) tests on interference systems have been passed, 8) machine power has been interrupted by control stop signals, emergency stop devices or by power disconnect, 9) zero speed systems give permission to unlatch and, 10) interference devices are fully deployed.
In order to better understand applicant""s invention there will be schematically illustrated and described systems employing motion detectors for indicating when the machine components have completed their run down and systems for testing the zero speed indicators without shutting the machine down. This may or may not include isolating the motion detector from the machine during testing depending on the system employed. In addition, an apparatus will be described wherein an interference device is inserted to prevent accidental resumption of motion after all motion has ceased when zero speed is indicated.
In order to better understand applicant""s invention there will also be described in detail hereinafter flow charts illustrating an example of a main routine for the testing of safeguarding devices and systems for guard closures as well as a number of subroutines. The subroutines include 1) a zero speed indicator test subroutine for in situ testing while the machine is running; 2) a zero speed indicator test subroutine for in situ testing during the speed run down phases caused by machine stop initiations; 3) a subroutine in which there is insertion of a motion interference device at the completion of the speed run down brought about by initiating stopping of the machine and 4) a subroutine for checking the fulfillment of the necessary conditions for unlatching a guard closure.